In recent years, necessity of global environment conservation is widely known, and a cogeneration apparatus serving as a privately-owned electrical power facility which performs electric power generation, hot-water supply, and the like by using an engine, as a power source, such as a gas engine using city gas or the like as fuel attracts attention. In the cogeneration apparatus of this type, a heat output generated by electric power generation cannot be often simultaneously consumed. From the viewpoint that energy is used without waste, a heat-demand-priority type apparatus which does not generate an amount of heat which cannot be consumed is proposed. For example, a cogeneration apparatus described in Japanese Patent Application Laid-open No. 2000-87801 has an electric power generation output linked with a commercial electric power system, receives electric power supply from the system in case of no heat load, and operates only when a heat request is made to improve operating efficiency. Japanese Patent Application Laid-open No. 2000-297963 proposes a heat-demand-priority type apparatus which further includes a hot-water supply tank as a buffer for heat output and heat demand and which temporarily accumulates an amount of heat as hot water in the hot-water supply tank when the heat output and the heat demand are not equal to each other. According to this apparatus, an amount of heat can be used through hot water depending on heat demand when the cogeneration apparatus does not operate to make it possible in order to reduce waste of heat energy.
Patent Document 1: JP 2000-087801 A
Patent Document 2: JP 2000-297963 A